The present invention concerns an arrangement for repeatedly feeding out fiber bundles with random fiber direction from a magazine roll of fiber thread, for example in the production of flock preforms for products made of thermosetting resin. The arrangement comprises feed devices for feeding the fiber threads from the magazine roll and cutting devices for cutting, the fiber into desired lengths. The feed devices comprise at least a first and a second pair of driven feed rollers placed in sequence, which feed rollers form nips for the fiber threads, and a pneumatically driven fiber-ejecting device placed downstream of the cutting device.
The production of fiber reinforced thermosetting resin products is difficult to automate since the quality of the product depends to a great extent on how the fibers are oriented with respect to how the product will be subjected to loading. Modern quality standards usually require a product to have an exact quantity of fibers that are oriented to obtain maximum strength without the fibers penetrating the product""s outer plastic layer.
It is customary to use very thin fibers, known as surfacing mat fibers in the outer fiber layer. This prevents the more robust fibers of normal thickness from penetrating the outer plastic layer of the thermosetting resin product. Such penetration would otherwise lead to the product having to undergo a costly manual after-treatment.
The aim of the present invention, is to produce an arrangement for feeding out thin fiber bundles, which bundles can be used as surfacing mat layers in the manufacture of thermosetting products, and which arrangement makes it possible to automate the addition of reinforcing fiber to a product, for example by using an industrial robot, so that flock preforms can be repeatably produced.
For this purpose the invention is characterized in that the first pair of feed rollers is driven at slightly lower feeding speed than the second pair of feed rollers, and that the fiber ejection devices include an oblong tube sleeve with air flow channels for directed turbulent air flow.